For transmitting sensor data to a central control unit (ECU) in a vehicle, peripheral sensors for occupant protection systems generally use current interfaces (e.g., PAS4, PSI5). In current interfaces of the latest generation (PSI5), bus operation, including multiple sensors on one receiver, is made possible with the aid of synchronization. A working clock pulse in the form of a voltage pulse is generated by the central control unit (ECU) for the synchronization function. This voltage pulse is detected by the sensors on the bus and identifies the start of a new cycle for data transmission. This voltage pulse is known as the synchronization pulse and is formed with the aid of current sources and current sinks, which charge and discharge the bus load. This voltage pulse is typically repeated every 500 μs.
In order for a synchronous bus system having one sensor or multiple sensors to function, it is important for the synchronization pulse to have a certain shape and a certain time characteristic for all possible bus configurations under all possible operating conditions. Therefore, with conventional synchronous bus systems, a trapezoidal synchronization pulse PT having a predefined edge steepness, as illustrated in FIG. 3, is generally used. The edge steepness here lies between an edge steepness of a first characteristic curve, which represents a lower limit Vu, and an edge steepness of a second characteristic curve, which represents an upper limit Vo. During synchronous operation of the bus, the trapezoidal shape of synchronization pulse PT results in increased electromagnetic emission (EME) in the frequency spectrum of the signal transmission due to the high harmonic content. This may be counteracted to a certain extent by a synchronization pulse PTr as illustrated in FIG. 4, for example, which has a trapezoidal shape having four rounded corners.
German Patent Application Publication No. DE 10 2009 001 370 A1 describes a reception device for receiving current signals, a circuit configuration having such a reception device and a method for transmitting current signals via a bus system. The reception device described there includes at least two bus connection devices for receiving current signals from multiple transmitters, each bus connection device being designed for connection to at least one bus connection, and a control device for outputting synchronization pulses to the bus connection devices for synchronization of the transmitters. The bus connection devices output the synchronization pulses to the multiple transmitters with at least one time offset relative to one another, the synchronization pulses each having a trapezoidal shape with rounded corners.